Can a battery charger be used to supply power to my black tank's macerating pump by connecting the charger's alligator clips to the pump's alligator clips?
My Sani-Con Tank Buddy RV waste pump only needs to be on approx. 2-5 minutes every week. The Owner's Manual says it requires a 12VDC with a minimum 20AMP dedicated power source so that leaves out using the RV's batteries!

So why can't you hook it to the batteries? Some battery chargers can supply 12V directly and some can't. You can try it and measure the voltage under load to see what it does. You are going to need a pretty hefty battery charger to power 20A. Batteries should be good for several times that for short periods of time. If you have a 100 AMP hour battery it should be able to power that pump for 5 hrs.

As Perry has noted you are unlikely to have good results operating the pump from a battery charger. There is no reason you can't use the batteries in the RV as long as the cables will reach, though that won't make for an especially convenient setup.

The cost and complexity of these systems is considerable. If you are new to RVing, you might want to consider using a standard gravity hose for waste disposal, or perhaps something like the Sewer Solution if you are dumping into the drain at your house.

The Mfg. states that I can hook directly to my battery, as long as it has a 20-amp breaker between the battery and the Sani-Con pump. But by hooking directly to my battery, I would be by-passing the breaker altogether! On the other hand, the Mfg. calls for the use of a "DEDICATED" battery but then there would be no involvement of a breaker at all. As you can see, I'm new to this and confused.

What they should be saying is a "dedicated circuit". Your pump draws 20A, which is a lot of current compared to an LED or a light bulb, but the battery(ies) can easily supply this for 10 minutes (or a hour or two).

Will this be permanently installed somewhere or is this a portable unit?

Can a battery charger be used to supply power to my black tank's macerating pump by connecting the charger's alligator clips to the pump's alligator clips?
My Sani-Con Tank Buddy RV waste pump only needs to be on approx. 2-5 minutes every week. The Owner's Manual says it requires a 12VDC with a minimum 20AMP dedicated power source so that leaves out using the RV's batteries!

The RV's batteries will supply far more than the requirements of the macerator, and will work just fine.

I don't use my macerator often, but have used an old battery charger to power it a number of times. My charger is only 10 amp rated, but the actual current to the macerator has been less than that.

However, most battery chargers made today have electronic systems that only turn the charge current on when the charger "sees" 12 volts from a battery with the polarity properly connected, so they will not work as a power supply. My charger is old school technology and does not have this problem.

One other thought, if anyone has an old "buzz box" univolt, they make excellent high current battery substitutes. It is about all they are good for, other than a boat anchor.